桃色欧文氏菌胞外多糖和根瘤菌的联合接种对紫花苜蓿苗期的促生作用

Growth-promoting effect of Erwinia persicina exopolysaccharide and Rhizobia combined inoculant on alfalfa seedlings

摘要:

【目的】 探究外援添加胞外多糖和根瘤菌联合接种剂对紫花苜蓿苗期生长的影响，为创新优化根瘤菌接种剂和紫花苜蓿提质增产提供理论依据。【方法】 以紫花苜蓿巨能551、桃色欧文氏菌 （Erwinia persicina）Cp2 胞外多糖（EPS-Cp2）和根瘤菌（Rhizobia）Gz5菌株为试验材料，设置 5个 EPS-Cp2浓度（0、0.6、0.9、1.2和1.5 g/L）联合Gz5（接菌量不少于108 CFU/mL）接种剂在水培条件下研究其对紫花苜蓿幼苗的促生作用。【结果】 随着EPS-Cp2浓度的增加，紫花苜蓿幼苗的鲜重、干重和株高均呈先增后降的变化趋势，在高于1.2 g/L EPS-Cp2浓度时，会对根长有显著的抑制作用。联合接种剂虽会显著抑制种子的发芽势，但对发芽率和发芽指数作用均并不显著；其不仅通过改善幼苗根系结构，显著促进根系生长和根部结瘤，还会提高幼苗叶片光合参数。此外，联合接种剂还显著提高了紫花苜蓿幼苗体内的SOD、CAT和DHA活性，使MDA、H2 O2 和O· 2 含量维持在幼苗正常生长的范围内。【结论】 0.6~1.5 g/L EPS-Cp2和Gz5联合接种剂可以有效地促进紫花苜蓿幼苗的生长和根部结瘤，且1.2 g/L的EPS-Cp2和Gz5联合接种剂对紫花苜蓿幼苗生长的促进效果最好，而EPS-Cp2 在联合接种剂的促生效果中发挥了主要作用。

Abstract:

【Objective】 This study aimed to investigate the effects of exogenous polysaccharide and Rhizobia combined inoculants on the growth of alfalfa seedlings，providing a theoretical basis for innovative optimization of Rhizobia inoculants and to improve the quality and yield of alfalfa.【Method】 Using alfalfa 'Juneng 551'，Erwinia persicina Cp2 exopolysaccharide （EPS-Cp2） and Rhizobia Gz5 strains as test materials，the effects of five concentrations ofEPS-Cp2 （0，0. 6，0. 9，1. 2 and 1. 5 g/L） combined with Gz5 （≥108 CFU/mL） on alfalfa seedling growth were studied under hydroponic conditions【Result】 The fresh weight，dry weight，and plant height of alfalfa seedlings increased initially withrising EPS-Cp2 concentrations but decreased when the concentration of eps-CP2 was exceeded 1. 2 g/L，which had a significant inhibitory effect on root length. While the combined inoculant reduced the germination potential of seeds，it did not significantly affect the germination rate or germination index. The combined inoculant notably enhanced root growth and nodulation by improving root structure increased photosynthetic parameters in seedling leaves，and significantly elevated SOD，CAT and DHA enzyme activities. Furthermore，the levels of MDA，H2 O2 and O· 2 in alfalfa seedlings were maintained within the normal growth range.【Conclusion】 Combined inoculants of 0. 6~1. 5g/LEPS-Cp2 and Gz5 effectively promoted the growth and root nodulation of alfalfa seedlings， with the optimal concentration of the combined inoculants of 1. 2g/L delivering the best effect on the growth of alfalfa seedlings. The growth-promoting effects were primarily attributed to EPS-Cp2 in the combined inoculant.